The present invention relates generally to an improved technique for conveniently adding highly effective migrating corrosion inhibitors to raw concrete, and including a technique for controllably and reliably adding such inhibitors to raw concrete mixes. The present invention utilizes a water soluble envelope or bag into which highly effective corrosion inhibitors are packaged, with the entire bag along with its contents being conveniently added to concrete mixes, including those mixes in the process of being blended in either stationary or portable mixers. Selected migrating corrosion inhibitors (MCI) comprising an alkali metal gluconate such as sodium gluconate and ammonium benzoate, and other dry inhibitors are blended and conveniently packaged in a water soluble bag, pouch or envelope in order to provide a measured and convenient method of adding such inhibitors to form complete concrete admixtures. These corrosion inhibitors, when added to the raw concrete mix, have been found to provide effective long-term protection for reinforcements including rebar as conventionally employed in concrete structures.
The formulations of the present invention are employed without reduction of the inherent strength of the concrete. Indeed, the strength, durability and appearance of the finished concrete are virtually unaltered, and when employed with a plasticizer, the mix remains fresh and plastic to permit more appropriate working.
In the past, certain types of migrating corrosion inhibitors have been blended with raw concrete in order to provide effective long-term rebar protection. While this form of addition has been effective, the entire process is improved, simplified and expedited when the MCI materials of the present invention are pre-packaged in containers so that the entire package may be added to and blended with the concrete mix. The present invention employs highly effective MCI materials which are packaged in water soluble bags or pouches, and thereby added at a known rate or in a predetermined quantity to concrete mix. As such, the MCI materials of the present invention are as well conveniently controlled, and rendered available for ultimate end use.
The bag containing the MCI chemicals is added to the raw concrete so that the ingredients become thoroughly mixed. Mixing is typically undertaken either on the site or in a central batching and mixing location with the fresh concrete being taken and delivered to the site and revolving drum ready-mix trucks.
In addition to those mixtures set forth herein, suitable MCI mixtures which are also well adapted to concrete are disclosed in U.S. Pat. No. 5,597,514 entitled "CORROSION INHIBITORS FOR REDUCING CORROSION IN METALLIC CONCRETE REINFORCEMENT", and assigned to the same assignee as the present invention. In addition to being highly effective as migrating inhibitors for the present application in concrete, these inhibitors have also been found to be soundly adapted for packaging in water soluble bags.